Incorporation of drilling cuttings into stable load-bearing structures

ABSTRACT

Cuttings from drilling through or into natural rock and/or soil can be incorporated into useful, high quality load-bearing structures such as vehicle roads and pads for deep drilling rigs. This process recycles a material previously regarded as valueless at best and often as a pollution hazard. The cuttings, optionally mixed with drilling mud and/or soil, are converted to the useful structures by pozzolanic and/or cementitious reactions after being mixed with suitable other materials and/or are bonded into the useful structures by asphaltic materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Priority under 35 U.S.C. § 119(e) from application Ser. No.60/311,439 filed Aug. 10, 2001 is claimed for this application.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] Drilling through or into natural soil and/or rock is performed ina variety of ways to serve practical ends. Any such drilling convertsinitially continuous solid soil and/or rock into particulate solidmatter called “drilling cuttings,” which have heretofore been generallyregarded in the art as waste material to be disposed of as inexpensivelyas possible. Hereinafter, the term “drilling cuttings” and any of itsgrammatical variations shall be understood to mean such cuttingsproduced by drilling through and/or into natural soil or rock.

[0004] For practical reasons, drilling through or into natural soiland/or rock is commonly divided into two kinds: “shallow” and “deep.”Relatively shallow drilling with a variety of means known in the art isused, for example, in construction of building foundations and miningexcavations and in making water wells in areas where the water table isno more than a few tens of feet below the natural soil surface. Shallowdrilling, simply because it is shallow, produces relatively lowpetroleum and/or natural gas often generates large volumes of cuttings.Therefore, even the most inexpensive possible disposition of thecuttings as waste, specifically burial of the cuttings in soil, oftenincurs a substantial expense.

[0005] Practical deep drilling normally requires more elaborateequipment than is usually used for shallow drilling. More specifically,deep drilling equipment normally comprises at least the following threeconceptual entities:

[0006] drilling means, which, after the first few meters of drilling arewithin the hole being drilled (the “borehole”) and are in physicalcontact with the solid soil and/or rock at the portion of the boreholethat is to be enlarged during the next interval of drilling, and which,when suitably driven, convert the volume of solid material thatcorresponds to the enlargement of the borehole during this particularinterval of drilling into particles sufficiently small to be readilyremoved from the borehole and transported to the earth's surface;

[0007] drilling driving means that supply the energy needed to cause thedrilling means to provide actual drilling; and

[0008] a fluid lubricant for the drilling means.

[0009] (Although these entities are conceptually distinct, the samephysical material may serve as all or part of two or more of them, andin practice the lubricant is probably more often than not also ahydraulic fluid that acts as part of the drilling driving means.) Thephrase “deep drilling” when used hereinafter in this specification shallbe understood to mean drilling performed by equipment comprising saiddrilling means, drilling driving means, and fluid lubricant for thedrilling means.

[0010] The currently most commonly used deep drilling means are varioustypes of rotary drill bits well known in the drilling art. In oncewidely practiced and still sometimes used “cable tool” drilling, thedrilling means are essentially a hammer that is repeatedly lifted anddropped within the borehole in order to deepen it. In some laboratoriestoday, laser light is being tested as a drilling means, and shock wavespropagated through air or other fluids could reasonably be used asdrilling means.

[0011] Typical deep drilling driving means may be: a solid structure ofpipe or cable connected mechanically to the drilling means and rotated,or alternatively lifted and dropped, by motive power supplied at thesurface so that the motion of the solid connecting structure ismechanically transferred to the drilling means; a combination of ahydraulic fluid, fluid transport means, and a pump that drives thehydraulic fluid, so that the motion of the hydraulic fluid, by itspassage through suitably designed passageways in a rotary drill bit,forces the components of the bit to move in a manner that converts anycoherent solid material adjacent to the rotary drill bit intoparticulates; a source of radiation that is absorbed by the surface of avolume of solid to be added to the volume of the borehole, the absorbingsolid surface and part of the solid underlying it being thereby rapidlyheated and caused to fracture by heating-induced expansion; and/or meansfor propagating mechanical shock waves through a fluid in contact withthe surface of a volume of solid to be added to the volume of theborehole.

[0012] The least expensive possible deep drilling lubricant is the airof the natural atmosphere, and this is actually used in practice in someinstances. Another established deep drilling lubricant is a foam of airin a continuous liquid phase, usually preponderantly of water. However,practical deep drilling for oil and/or natural gas in most locations inthe world that are now being explored requires use of a viscous liquidlubricant that comprises, preferably consists essentially of, or morepreferably consists of at least one continuous liquid phase and at leastone type of dispersed solid particles, most often a clay (such as sodiummontmorillonite) that has a sufficiently fine particle size andsufficiently hydrophilic particle surfaces that the clay spontaneouslydisperses in most aqueous based liquids. (In oil-based lubricants andsome water-based ones, additional surfactants are usually added topromote suspension of the clay and/or other solid constituents such ashigh density, water-insoluble “wetting agents” in the fluid.) Additionaldetailed information about deep drilling fluids is given in, e.g., H. C.H. Darley and George R. Gray, Composition and Properties of Drilling andCompletion Fluids, 5th Ed. (Gulf Publishing Co., Houston, 1988), theentire disclosure of which, except for any part that may be contrary toan explicit statement herein, is hereby incorporated herein byreference. This deep drilling lubricant, when preponderantly liquid andoften even when preponderantly gaseous, is generally called “drillingmud” or simply “mud” by those who use it, and the word “mud” when usedbelow in this specification shall be understood to mean deep drillingmud or another deep drilling fluid unless expressly stated to thecontrary or required by the context.

[0013] Mud normally is pumped continuously into and flows continuouslyout of a borehole whenever deep drilling is underway. The mud flows intoand out of the borehole through separate passageways that are disposedso as to insure that mud pumped into the borehole must reach the nearvicinity of the drilling means that is actually cutting a boreholedeeper during drilling before the mud can enter any passageway throughwhich mud flows out of the borehole during drilling. The mud serves tocool and lubricate the drilling means and to remove from the boreholesoil and/or rock in the form of particles cut by the drilling means,such particles being commonly called “cuttings”. (If these cuttings werenot removed from the borehole, they would eventually clog the drillingmeans and make continued drilling impossible.)

[0014] The oufflowing mixture of mud and cuttings from deep drilling isnormally subjected to at least one separation process intended toseparate the relatively large particle size cuttings from the relativelyfine clay and any other suspended particles deliberately added as partof the drilling mud before it flows into the borehole. The cuttings fromthis separation are generally more or less wet with the fluid phase ofthe mixture of mud and cuttings from which they were separated and maycontain relatively small portions of the dispersed and/or dissolvedsolids deliberately added to the drilling mud before it flows into theborehole. Also, the cuttings as thus separated may be and often areremixed with all or part of the drilling mud used when deep drilling ofa particular hole has been completed. The solids volume of the cuttingsor mixture of the cuttings with no longer needed drilling mud is usuallyat least several hundred cubic meters for each well drilled to a depthof five thousand meters.

[0015] A major object of this invention is to convert and/or incorporatemixtures of drilling cuttings, optionally mixed with other constituentssuch as those of deep drilling mud, into stable load-bearing structures.

BRIEF SUMMARY OF THE INVENTION

[0016] It has been found that drilling cuttings and mixtures of thecuttings with drilling mud can be converted and/or incorporated intoexcellent high-load-bearing civil engineering structures such as vehicleroads and drilling pads by one or more processes as described in detailbelow. Embodiments of the invention include processes for suchconversion, extended processes including additional operations that maybe conventional in themselves, and the load-bearing structures made by aprocess according to the invention.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

[0017] A shaped load-bearing structure according to the invention ismade by a process comprising, preferably consisting essentially of, ormore preferably consisting of, the following operations:

[0018] (1) forming a particulate mixture comprising drilling cuttings;and

[0019] (2) at least one of groups (2.1) and (2.2) of suboperations, saidgroup (2.1) comprising suboperations of:

[0020] (2.1.1) mixing said particulate mixture comprising drillingcuttings in a specified proportion with at least one material selectedfrom the group consisting of:

[0021] (A) quicklime;

[0022] (B) hydrated lime;

[0023] (C) Portland Cement;

[0024] (D) Class C fly ash;

[0025] (E) cement kiln dust;

[0026] (F) lime kiln dust;

[0027] (G) Class F fly ash; and

[0028] (H) other pozzolans to form a cementitious second mixture;

[0029] (2.1.2) forming said cementitious second mixture into the shapeand size of the desired load-bearing structure; and

[0030] (2.1.3) causing the shaped and sized second mixture formed insuboperation (2.1.2) to undergo a pozzolanic reaction to form saidload-bearing structure; and said group (2.2) comprising suboperationsof:

[0031] (2.2.1) mixing said particulate mixture comprising drillingcuttings in a specified proportion with at least one of foamed asphaltand emulsified asphalt to form an asphaltic second mixture;

[0032] (2.2.2) forming said asphaltic second mixture into the shape andsize of the desired load-bearing structure; and

[0033] (2.2.3) causing the shaped and sized asphaltic second mixtureformed in suboperation (2.2.2) to form the load-bearing structure byremoval from said shaped asphaltic second mixture of a sufficientfraction of the gas dispersed in any foamed asphalt incorporated intosaid second mixture and of the liquid continuous phase in which anyemulsified asphalt incorporated into said shaped second mixture isemulsified.

[0034] Any material as described above that is mixed with theparticulate mixture comprising drilling cuttings in suboperation (2.1.1)or (2.2.1) is denoted herein as a “stabilizer.” Following are thebelieved mechanism of stabilization for each stabilizer and the basicadvantages and limitations for each of the types of stabilizers listedabove, those types of stabilizers listed explicitly above beingpreferred over other pozzolanic stabilizers.

[0035] QUICK LIME AND HYDRATED LIME

[0036] Whether hydrated lime, i.e., Ca(OH)₂, or quick-lime, i.e., CaO,is selected as a source of stabilization, it is believed that hydratedlime is more effective for stabilization. Therefore, if quicklime isselected as the source of stabilization, at an early stage during theformation of the second mixture as described in suboperations (2.1.1)and (2.2.1) above, the quicklime preferably is transformed to hydratedlime through reaction with adequate quantities of water. This water mayderive from the particulate mixture comprising drilling cuttings asdescribed above or may be added separately. Since the gram-molecularweight of Ca(OH)₂ is approximately 74 and the gram-molecular weight ofCaO is approximately 56, the minimum mass of water required forhydration is 34 percent of the mass of the CaO to be hydrated.Practically, however, hydration, also called “slaking,” of quicklime isnot usually 100 percent efficient within a reasonable time. Under mostconditions, therefore, the mass of the water available for slaking anymass of quicklime used as a stabilizer in a process according to theinvention preferably is at least, with increasing preference in theorder given, 50, 60, 70, 80, 90, or 99% of the mass of the quicklime.

[0037] Lime is believed to stabilize primarily the clay fraction of thefirst mixture of mud and cuttings to be stabilized with which it ismixed to form a second mixture as described above. Therefore, when limeis an important or the sole component of the stabilizing agent used in aprocess according to this invention, the particulate mixture comprisingdrilling cuttings to be stabilized preferably comprises clay as apercentage of its solids content that is at least, with increasingpreference in the order given, 2, 4, 6, 8, 10, 12, 15, 20, or 25%.Independently, the particulate mixture comprising drilling cuttings tobe stabilized with lime in a process according to the inventionpreferably has a Plasticity Index (hereinafter usually abbreviated as“PI” and determined according to American Society for Testing andMaterials (hereinafter usually abbreviated as “ASTM”) Procedure D-4318)that is at least, with increasing preference in the order given, 3, 5,7, 9, 11, 13, 15, 20, 25, or 30 percent. Lime is believed to react withthe clay in the high pH environment created when lime and water aremixed. In this environment, the silica and alumina contents of the clayare believed to become sufficiently soluble, as pozzolans, to react withthe calcium and water to form calcium-silicate-hydrates andcalcium-aluminate-hydrates that are cementitious products. (A pozzolanis defined as a high surface area siliceous or alumino-siliceousmaterial that in the presence of an alkaline earth-containing alkalisuch as lime produces a cementitious reaction.) This postulatedreaction, along with calcium exchange on clay surfaces, reduces theplasticity of, improves the workability of, improves the drying anddrainage of, and provides a substantial strength gain for, theparticulate mixture comprising drilling cuttings to be stabilized.

[0038] The major advantages of lime are that: it vastly improves theworkability of highly plastic mixtures comprising cuttings to bestabilized; and it reacts slowly enough to allow plenty of mixing time-up to four days. The major limitation is that lime does not react withsoils that do not contain a reactive clay fraction. Therefore, lime isnot reactive with gravelly and sandy soils without clay. Lime may not bereactive with sandy, silty-sandy, and silty soils without reactive clay.However, combinations of lime and fly ash can be effectively used tostabilize these soils.

[0039] Portland Cement

[0040] The basic reactions in stabilization with Portland Cement(hereinafter usually abbreviated as “PC”) stabilization are believed tobe the cementitious, hydration reaction that occurs when calciumsilicates and calcium aluminates present in the Portland Cement hydratewith added water. The strength gain is independent of soil mineralogy,e.g., whether any clay is present in the soil. However, some pozzolanicreaction between lime released during the cementitious reaction and anyclay that is present in the particulate mixture comprising drillingcuttings to be stabilized can and is believed to occur. Portland Cementprovides workability and strength improvements similar to those achievedwith lime. The major differences are that: PC usually works better withlow PI, granular soils, whereas lime works better with higher PI, clayeysoils; strength gain with PC is quicker than with lime; and PC willusually provide a higher final strength than lime in any structure madeby stabilization in a process according to this invention. The fasterstrength gain can be either an advantage or a disadvantage, depending oncircumstance; it can be an advantage in meeting a short constructionschedule, but the construction/shaping time is usually limited to fourhours after mixing in order to avoid significant strength loss. A secondlimitation is a greater prevalence of significant shrinkage cracking instructures stabilized with high percentages of PC.

[0041] Class C Fly Ash

[0042] Class C fly ash is a non-combustible residue of coal. Thisresidue is composed primarily of high surface area silicates andaluminates and often contains calcium from calcium oxide naturallypresent in the coal and/or added to abate air pollution by reacting withgaseous oxides of sulfur generated by the combustion of some coal. Whenwater is added to Class C fly ash, any silicates and aluminates in thefly ash that have been fused with calcium oxide are believed to react aswith PC to form cementitious products, while the silicates andaluminates that have not previously been fused with lime are believed toreact as pozzolans if an outside source of lime is added. Class C flyash is accordingly believed to stabilize cementitious second mixtures asdescribed above through combined processes of hydration and pozzolanicreactions that result in improved workability of the second mixturesduring shaping and sizing and in increased shear strength in the curedstructure.

[0043] Fly ashes are quite variable and source dependent. Class C flyash for use in a process according to this invention preferably has thefollowing characteristics, each of these characteristics beingindependently preferred and combinations of the characteristics beingstill more preferred, the preference being greater the greater thenumber of preferred characteristics combined:

[0044] the percentage of the mass of the fly ash retained on a No. 325sieve preferably is not more than, with increasing preference in theorder given, 34, 32, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6,4, or 2%;

[0045] the total content of SiO₂+Al₂O₃+Fe₂O₃ preferably constitutes apercentage of the total mass of the fly ash that is at least, withincreasing preference in the order given, 50, 60, 65, 70, 75, 80, 85,90, 95, or 99%;

[0046] the total content of sulfur, measured as its stoichiometricequivalent as SO₃, preferably is not more than, with increasingpreference in the order given, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5,0.3, or 0.1%; and

[0047] the loss on ignition of the fly ash preferably is not more than,with increasing preference in the order given, 10, 8, 6, 4, 2.0, 1.5,1.0, 0.5, 0.3, or 0.1%.

[0048] Class C fly ash is similar to PC in its ability to provide highstrength, its ability to provide stabilization even in the absence ofclay in the particulate mixture comprising drilling cuttings to bestabilized, and in its fast strength development. The principaladvantage of Class C fly ash is that it can be considerably lessexpensive than PC or lime if available from a source near where aprocess according to the invention is performed, and the principaldisadvantage of Class C fly ash is its variability in setting time,which requires more frequent testing than with PC except in relativelyrare instances where a sufficiently large supply of the fly ash withconsistent properties is available.

[0049] Combinations of Lime and Fly Ash

[0050] Class F fly ash is a more or less pure pozzolan which containslittle or no alkaline earth metal content. Lime reacts with Class F ashas it does with clay to produce a pozzolanic reaction which can be ofsubstantial value in strength development in a shaped and sizedsecondary mixture as described above. Class F ash and lime can beeffectively used together to stabilize mixtures of mud and cuttings witha wide range of mineralogical contents ranging from clays to sands andgravels. Since a pozzolan is contributed by the ash, clay is notrequired to react with the lime.

[0051] Like Class C ash, Class F ash is variable from source to source.Class F fly ash for use in a process according to this inventionpreferably has the following characteristics, each of thesecharacteristics being independently preferred and combinations of thecharacteristics being still more preferred, the preference being greaterthe greater the number of preferred characteristics combined:

[0052] the percentage of the mass of the fly ash retained on a No. 325sieve preferably is not more than, with increasing preference in theorder given, 34, 32, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6,4, or 2%;

[0053] the total content of SiO₂+Al₂O₃+Fe₂O₃ preferably constitutes apercentage of the total mass of the fly ash that is at least, withincreasing preference in the order given, 70, 75, 80, 85, 90, 95, or99%;

[0054] the total content of sulfur, measured as its stoichiometricequivalent as SO₃, preferably is not more than, with increasingpreference in the order given, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5,0.3, or 0.1%;

[0055] the loss on ignition of the fly ash preferably is not more than,with increasing preference in the order given, 10, 8, 6, 4, 2.0, 1.5,1.0, 0.5, 0.3, or 0.1%; and

[0056] the unconfined compressive strength (hereinafter usuallyabbreviated as “UCS”), measured as described below, preferably is atleast, with increasing preference in the order given, 800, 850, 900,950, 1000, 1050, 1100, 1, 1200, 1250, 1300, 1350, 1400, 1450, or 1500pounds per square inch (hereinafter usually abbreviated as “psi”).

[0057] The unconfined compressive strength of the fly ash is measured onsamples that have previously been mixed with lime and/or Portland Cementin the same proportion between the fly ash and lime and/or PortlandCement as is intended for the combination to be used in stabilization.Tests on these mixtures are performed in accordance with ASTM ProcedureC-593 to determine the UCS value.

[0058] Combinations of Class F fly ash and lime have advantages anddisadvantages similar to those of lime, except that: the need forreactive clay in the particulate mixture comprising drilling cuttings tobe stabilized is removed by using Class F fly ash; the variability ofcharacteristics of all fly ash is introduced; and the method ofapplication can be varied to advantage in some instances: Lime can beadded first to clay-containing mixtures, with the fly ash added later.The initial mixing of lime with the clay will reduce plasticity andimprove workability while the later addition of fly ash will enhancestrength. This may be superior to lime stabilization alone in mixturesof mud and cuttings to be stabilized, which, even though they maycontain clay, do not react rapidly enough with lime to producesufficient pozzolanic strength development for the purpose of a processaccording to this invention.

[0059] Combinations of Class C or Fluidized Bed Fly Ash and PortlandCement

[0060] These combinations are particularly advantageous in two-stageprocesses according to the invention, in which the fly ash is used as adrier in the first stage and the cement as an activator in the secondstage.

[0061] Other Cementitious and Pozzolanic Stabilizers

[0062] Besides lime, PC, and fly ash, other cementitious and pozzolanicstabilizers which may be candidates for stabilization in a processaccording to this invention include cement kiln dust (hereinafterusually abbreviated as “CKD”) and lime kiln dust (hereinafter usuallyabbreviated as “LKD”). These materials are by-products of cement andlime manufacture, respectively. CKD and LKD are similar to a Class C flyash in that they both contain some self-cementing calcium-silicate(hereinafter usually abbreviated as “CS”) and calcium-aluminate(hereinafter usually abbreviated as “CA”) compounds. However, both typesof kiln dust may have considerable free lime, “free lime” being definedfor this usage as the total amount of calcium hydroxide and calciumoxide, both measured as their stoichiometric equivalent as CaO, that arepresent in the material in a form free to react cementitiously withadditional silicates and/or aluminates that may be mixed with thematerial. LKD is generally higher in free lime and lower in CS and CAproducts than CKD. The only advantage of CKD or LKD over lime, PC, orfly ash is a lower cost. To provide a substantial cost advantage in aprocess according to this invention, CKD and/or LKD usually must belocally available near the process site. Both CKD and LKD are quitevariable.

[0063] Asphalt Emulsions and Foams

[0064] Asphalt emulsions consist essentially of fine particles ofasphalt emulsified in water. The emulsion is a sufficiently lowviscosity liquid to be mixed with a particulate mixture comprisingdrilling cuttings to be stabilized at normal ambient field temperatures(i.e., from about 0 to 50° C.), whereas a normal unemulsified asphaltwould have to be heated to around 300° C. in order to mix intimatelywith soil or aggregate. The emulsified particles of asphalt preferablyhave an average particle size (largest linear dimension) that is atleast, with increasing preference in the order given, 0.2, 0.5, 0.7,1.0, 1.2, 1.4, 1.6, 1.8, or 2.0 micrometres (hereinafter usuallyabbreviated as “m”) and independently preferably is not more than, withincreasing preference in the order given, 30, 20, 15, 13, 11, 9, 7, or 5m. Dispersion in water is maintained by using at least one emulsifyingagent, the emulsifying-effective moieties of which may have a positiveor a negative charge or be electrically neutral. Ordinarily, cationicemulsions (i.e., those in which the emulsified asphalt particles have apositive charge) are preferred for use with alkaline mixtures of mud andcuttings to be stabilized, while anionic emulsions in which theemulsified asphalt particles have a negative charge are preferred if theparticulate mixture comprising drilling cuttings to be stabilized areacidic. However, climatic conditions also affect preferences because ina high humidity environment, an anionic emulsion will not normally cureproperly, and curing of emulsions is very important to their success.Curing involves first properly coating the aggregate or soil with theemulsion and then removing the water in which the asphalt had beendispersed from the asphalt by draining and/or evaporating the water andleaving behind an asphalt coating of the aggregates. Adequate curingoccurs when the proper asphalt emulsion is selected and properconstruction methods are used to effect aeration of the mixture duringmixing. The residual asphalt then coats the aggregate to provide acohesive “glue” which in turn provides stability and durability to themixture.

[0065] Asphalt stabilization may, in some circumstances, be cheaper thanchemical stabilization. Asphalt is often preferred for stabilizingrelatively rare mixtures of mud and cuttings to be stabilized that havelittle or no plasticity and/or have such a high organic content thatthey cannot be stabilized with economically practical amounts ofpozzolanic or cementitious materials. Foamed asphalt and emulsifiedasphalt should produce essentially the same result. However, thetechnology for the use of foamed asphalt is not widely developed.

[0066] A major limitation with asphalt stabilization is that if or whenit is desired to recycle a structure made in a process according to thisinvention with asphalt stabilization to its original or near originalstate, recycling will usually be more complicated and correspondinglymore expensive because of the presence of the organic binder. On theother hand, calcium-based pozzolanic stabilizers can be recycled to anear virgin state by pulverization and mixing. The material will retaina relatively high pH, between about 8 and 11, but this can be reducedthrough dilution (mixing with virgin soil) if necessary. If the initialpH is near the higher end of this range, the pH will even bespontaneously reduced, at least in well-aerated parts of the recycledmaterial, by gradual conversion of more alkaline calcium-containingsubstances to calcium carbonate by reaction with atmospheric carbondioxide.

[0067] Because of the highly variable nature of the particulate mixturescomprising drilling cuttings to be stabilized and of some of thestabilizers used (the fly ashes and kiln dusts), the preferred amountsof stabilizers can be explicitly specified herein only in rather broadterms as shown in Table 1 below for the most important and preferredsingle and combination stabilizers. However, with minimalexperimentation that is well within ordinary skill in the art,considerably narrower preferences for each particular instance can bereadily determined by one of the testing protocols set forth below. Themost desirable stabilizer(s) to be tested initially can be readilydetermined by those skilled in the art by consideration of theadvantages and disadvantages of the various stabilizers as describedabove, the required civil engineering properties of the load-bearingstructure to be made in a process according to the invention, and thecosts of the various stabilizers at the site of the fabrication of thestructure. TABLE 1 BROAD PREFERENCES FOR AMOUNTS OF PREFERREDSTABILIZERS TO BE USED Preferred Amount of Stabilizer, as a Percentageof Solids in the Stabilizer to Solids in the Particulate MixtureComprising Drilling Stabilizer Cuttings to Be Stabilized Portland Cement(as the At least, with increasing preference in the order given, 0.5,1.0, 1.5, 2.0, 2.5, sole stabilizer) or 2.9% and independentlypreferably not more than, with increasing preference in the order given,15, 12, 10, 8, or 6.0% Lime (as the sole At least, with increasingpreference in the order given, 1.0, 2.0, 2.5, 3.0, 3.5, stabilizer) or4.0% and independently preferably not more than, with increasingpreference in the order given, 20, 15, 12, 10, or 8% Lime and fly ash(as the Lime that is at least, with increasing preference in the ordergiven, 0.2, 0.5, sole stabilizers) 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, or 2.0%and independently preferably is not more than, with increasingpreference in the order given, 9, 7, 5, or 3%; fly ash that is at least,with increasing preference in the order given, 0.2, 0.5, 0.8, 1.0, 1.2,1.4, 1.6, 1.8, or 2.0% and independently preferably is not more than,with increasing preference in the order given, 20, 17, 14, 12, 10, 8, or6%; and, independently, a ratio of fly ash to lime that is at least,with increasing preference in the order given, 0.3:1.00, 0.5:1.00,0.7:1.00, or 0.9:1.00 and independently preferably is not more than,with increasing preference in the order given, 5:1.00, 3.0:1.00,2.5:1.00, or 2.0:1.00 Class C and/or fluidized Fly ash that is at least,with increasing preference in the order given, 0.2, 0.5, bed fly ash andPortland 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, 3.6, 4.0, 4.4, or 4.8% andindependently Cement (as the sole preferably is not more than, withincreasing preference in the order given, 50, stabilizers) 35, 30, 25,or 20, 17, 14, 11, or 9%: Portland Cement that is at least, withincreasing preference in the order given, 0.5, 0.8, 1.0, 1.2, 1.4, 1.6,1.8, 2.0, 2.2, 2.4, 2.6, or 2.8% and independently preferably is notmore than, with increasing preference in the order given, 15, 10, 8.5,8.0, 7.5, 7.0, or 6.5%; and, independently, a ratio of fly ash to cementthat is at least, with increasing preference in the order given,0.10:1.0, 0.20:1.00, 0.30:1.00, 0.35:1.00, 0.40:1.00, or 0.45:1.00 andindependently preferably is not more than, with increasing preference inthe order given, 10:1.00, 8.0:1.00, 7.0:1.00, 6.0:1.00; 5.0:1.00,4.5:1.00, 4.0:1.00, 3.5:1.00, 3.2:1.00, 3.0:1.00, or 2.8:1.00. Class Cfly ash, lime At least, with increasing preference in the order given,0.5, 1.0, 1.5, 2.0, 2.5, kiln dust, and/or cement or 3.0% andindependently preferably not more than, with increasing kiln dust (asthe sole preference in the order given, 30, 25, 20, 15, or 10%stabilizer(s)) Asphalt, emulsified or At least, with increasingpreference in the order given, 0.5, 1.0, 1.5, 2.0, 2.5, foamed or 3.0%and independently preferably not more than, with increasing preferencein the order given, 25, 20, 15, 12, 10, or 8%

TEST PROTOCOLS Preliminary Tests—Visual Evaluation and Concentrations ofInterfering Constituents

[0068] The major objectives of visual evaluation are to estimate themoisture content of the particulate mixture comprising drilling cuttingsto be stabilized, this moisture content being normally quite high when amud with an aqueous liquid continuous phase is used, and to determinethe presence or absence in the particulate mixture comprising drillingcuttings to be stabilized of any foreign, non-soil-like material such asorganics, salt crystals, especially sulfate salts, and/or the like. Thusthe visual identification screens the material for any constituents thatare unusual and/or require special stabilization strategies.

[0069] Sulfates can interfere with pozzolanic reactions and cementitiousreactions when calcium-based stabilizers are used, causing a severelyexpansive reaction and loss of density and often strength. For thisreason, it is necessary to screen the cuttings for the presence ofsoluble sulfates. If soluble sulfates are found to be less than or equalto 3 parts per thousand by mass of the solids content of the particulatemixture comprising drilling cuttings to be stabilized, this unit ofconcentration being hereinafter usually abbreviated as “ppt”, there isno significant risk of these adverse effects from sulfates duringstabilization. (The concentration of sulfates preferably should bedetermined on the basis of Texas Department of Transportation TestMethods TEX-620-J and TEX-619-J. The partitioning of soluble sulfatesfrom the cuttings that is part of these test procedures preferably isdone with ten parts water to one part soil.) If soluble sulfates arepresent in a higher concentration than 3 ppt, there is some risk of suchadverse effects. Nevertheless, a process according to the invention canstill be used to stabilize high sulfate mixtures. For example, a highlysulfate tolerant type of Portland Cement can be used. Additional detailson this and other methods of coping with high sulfate content soiland/or rock are given in Little, “The Effect of Sulfates on Lime-SoilInteractions” in Handbook for Stabilization of Pavement Subgrades andBase Courses with Lime (Candle-Hunt Publishing Company, Dubuque, Iowa,1995), pp 51-52 and references cited therein, and in Searcher, S. L. andLittle, D. N., “Microstructural Stability of Sulfate-ContaminatedCrushed Concrete Treated with Cementitious Materials”, 1999 AnnualMeeting of the Transportation Research Board, all of which, except forany part which may be inconsistent with any explicit statement herein,are hereby incorporated herein by reference.

[0070] It is also known that organic material in excess of one percentby weight may be deleterious to pozzolanic and cementitious reactions incalcium-based stabilizers. If organics are present in levels thatinterfere with calcium-based stabilization, they will prevent strengthdevelopment. Therefore, the simplest way to evaluate the effect oforganics is to assess the rate and level of strength gain, a test thatis preferred for other purposes in any event and is described below.However, even though fairly high concentrations of organic material maybe tolerated in the particulate mixture comprising drilling cuttingsprovided in operation (1) as described above of a process according tothis invention, they will require larger amounts of calcium-basedstabilizer, and therefore be more expensive to treat, whenevercalcium-based stabilizers are used. Accordingly, the concentration oforganic material in the particulate mixture comprising drilling cuttingsprovided in operation (1) as described above of a process according tothis invention that employs group (2.1) of suboperations as describedabove preferably does not exceed, with increasing preference in theorder given, 15, 13, 11, 9, 7, 5, 3, or 1% by mass of said particulatemixture comprising drilling cuttings.

[0071] If a mixture desired to be treated according to the inventioncontains too much of sulfate, organic material, or any other constituentthat interferes with attaining the desired degree of stabilization, itmay nevertheless be treated by a process according to this invention bydiluting the initially unsuitable mixture with other sources ofparticulate rock and/or soil in sufficient quantity to bring theconcentrations of interfering material to a adequately low level in thediluted mixture.

[0072] One of the most common “interfering constituents” of a mixture tobe treated in a process according to this invention is water fromaqueous based drilling muds. This particular constituent, when presentin a mixture desired to be utilized in a process according to theinvention, is rarely if ever preferably reduced in concentration bydilution with another source of soil and/or rock. Instead, any largeexcess of water is preferably separated from the mixture by a lessexpensive technique, such as allowing the suspensions to settle anddrawing off accumulated water from above the settled bed of solids,spreading the wet mixture over a large outdoor area to promoteevaporation of the water, mixing with a solid drying agent, or the like.A particularly preferred technique, when the concentration of water inthe mixture and the nature of the soil and/or rock to be treated aresuitable, is to utilize a relatively inexpensive drying agent, such asfly ash and/or kiln dust, that also has a stabilizing effect asdescribed above. Any such material added should be regarded as part ofthe stabilizer when the amount of stabilizer is selected along theguidelines in Table 1. This technique is particularly advantageous whenmixtures of lime with fly ash and/or kiln dust are to be used as thepreponderant stabilizer, because the lime can be added at a later stageof mixing, when it is not so readily bound by excessive amounts of waterin the mixture to be stabilized and thereby prevented, or at leastdelayed, from promoting desired pozzolanic stabilization reactions.

Mixture of Cutting with Other Sources of Particulate Rock and/or Soilfor Purposes other than Dilution of Interfering Constituents

[0073] Dilution of cuttings with other sources of particulate soiland/or rock is a very useful supplemental technique in a processaccording to the invention in many instances, even when no dilution isrequired to reduce the concentrations of interfering substances. Forexample, often suitable soil is available at very low cost in the nearvicinity of a site where a structure is to be built by a processaccording to the invention. In such an instance, the cost of such astructure can often be considerably reduced by mixing some low cost soilwith the cuttings, because most naturally formed soils will need lessstabilizer per unit volume than most cuttings to be used in a processaccording to the invention, and the stabilizer is usually more costlythan either cuttings or natural soil. Furthermore, a mixture of naturalsoil and cuttings often forms a stronger structure in a processaccording to the invention than could be obtained from stabilizingnearby natural soil alone with the same amount of stabilizer. Stillfurther, of course, one object of the invention is to convert drillingcuttings to useful structures, particularly when such conversion willreduce potential liability for environmental pollution by the cuttings.Accordingly, it is preferred that particulate rock and/or soil producedby drilling constitute at least, with increasing preference in the ordergiven, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by mass of the particulatemixture comprising drilling cuttings provided in operation (1) asdescribed above of a process according to this invention, unless the useof such a high fraction of cuttings leads to results inconsistent withother preferences expressed herein for characteristics of the finishedstructures built by a process according to the invention. (For example,the use of cuttings and stabilizer only in a structure built by aprocess according to the invention could in some cases result in astructure more susceptible to cracking or other deterioration duringaging of the structure than if some other source of particulate rockand/or soil were incorporated into the structure.)

[0074] Alternatively or additionally, the fraction of cuttings in theparticulate mixture comprising drilling cuttings provided in operation(1) as described above of a process according to this inventionpreferably is such that the unconfined compressive strength of astructure built by a process according to the invention is greater by atleast, with increasing preference in the order given, 3, 6, 9, 12, 15,18, 21, 24, 27, or 30 percent than the unconfined compressive strengthof a reference structure built by a process that is identical, exceptthat all of the cuttings included in the particulate mixture comprisingdrilling cuttings provided in operation (1) as described above for theprocess according to this invention are substituted by an equal volumeof the constituents other than cuttings that are present in saidparticulate mixture.

Lime and/or Hydrated Lime Stabilization

[0075] The degree of stabilization normally desired requires that iflime is the sole or greatly predominant stabilizer, a sufficient amountof lime be added not only to reduce plasticity of clay fines (improveworkability) but also to achieve a substantial pozzolanic reactionbetween clay fines and hydrated lime. This test protocol ensures that anappropriate amount of lime is added to achieve the desired engineeringproperties.

[0076] Step 1

[0077] Determine the pH of mixtures of the particulate mixturecomprising drilling cuttings to be stabilized with lime in amountsvarying in Ca(OH)₂ content from 0 to 10 percent. Select a target limecontent in accordance with ASTM C-977.

[0078] Step 2

[0079] Prepare samples according to ASTM D-698 to determine a predictedoptimum moisture content for samples with the target percentage ofhydrated lime determined in Step 1, with at least one of 1.0 and 2.0percent below, and with at least one of 1.0 and 2.0 percent above thetarget lime content determined in Step 1. Samples should be intimatelymixed with the specific type of lime and/or hydrated lime intended foruse in a process according to this invention and allowed to mellow fortwo hours prior to compaction.

[0080] Step 3

[0081] Fabricate three samples at and/or within 2% of the predictedoptimum moisture content determined in Step 2 for each trial limecontent. Condition the samples at 100 percent relative humidity and at atemperature of 40° C. (The approximate 100 percent relative humidityenvironment is difficult to achieve in many high temperature chambers.In order to maintain the level of moisture required for pozzolanicreaction and cementitious reaction, it is advisable to wrap the samplein plastic and then to place the sample with approximately 10 grams ofwater in a readily sealable and unsealable moisture-proof plastic bag.)

[0082] Step 4

[0083] Determine the UCS of the samples prepared in Step 3 after thesesamples have been compacted in accordance with ASTM D-698. ASTMProcedure D-5102 is used to determine UCS. The test should be performedon the standard-sized samples used in compaction density evaluation.Prior to UCS testing, the samples are wrapped in a fibrous geofabriccapable of transporting moisture along the circumference of the sample,placed on a porous stone covered to the top with water, and allowed toabsorb moisture through capillary soak for a period of 24 hours.

[0084] Step 5

[0085] Plot the compressive strengths of the three samples at each ofthe three lime contents determined in Step 4 on a chart of compressivestrength versus stabilizer content. Select the lime content thatprovides both the highest compressive strength and an acceptablecompressive strength based on the section below titled, “TargetEngineering Properties and Structural Thickness Requirements”.

Portland Cement Stabilization

[0086] Step 1

[0087] Select three trial PC contents based on Table 1. If thesestabilizer contents do not provide acceptable strength, then additionaltrials may be made.

[0088] Step 2

[0089] Prepare samples according to ASTM D-698 to determine a predictedoptimum moisture content for a sample with each PC percentage selectedin Step 1. The particulate mixture comprising drilling cuttings to bestabilized should be intimately mixed with PC and then immediatelycompacted.

[0090] Step 3

[0091] Fabricate three samples at and/or within 2% of the predictedoptimum moisture content determined in Step 2 for each trial PC content.Cure the samples by placing them in a sealed plastic bag and place thebagged samples in a curing room at a temperature of 25° C. for 7 days.

[0092] Step 4

[0093] Determine the UCS of the samples fabricated in Step 3 by the sameprocedures as for Step 4 under the heading “Lime and/or Hydrated LimeStabilization” above.

[0094] Step 5

[0095] Plot the compressive strengths of the three samples at each ofthe three PC contents on a chart of compressive strength versusstabilizer content. Select the PC content in the same manner as used forselecting lime content in Step 5 under the heading “Lime and/or HydratedLime Stabilization” above.

Class C Fly Ash, Lime Kiln Dust, and/or Cement Kiln Dust Stabilization

[0096] Step 1

[0097] Select three trial ash and/or dust contents from Table 1. Ifthese stabilizer contents are not satisfactory, then additional testingmay be required.

[0098] Step 2

[0099] Prepare samples according to ASTM D-698 to determine a predictedoptimum moisture content for a sample with each percentage of ash and/ordust selected in Step 1. Samples should be intimately mixed with the ashand/or dust and then compacted immediately.

[0100] Step 3

[0101] Fabricate three samples at and/or within 2% of the predictedoptimum moisture content determined in Step 2 for each trial ash and/ordust content. Cure the samples by placing them in a sealed plastic bagand placing the bagged samples in a curing room at a temperature of 25°C. for 7 days.

[0102] Step 4

[0103] Determine the UCS of the samples cured in Step 3 by the sameprocedures as for Step 4 under the heading “Lime and/or Hydrated LimeStabilization” above.

[0104] Step 5

[0105] Plot the compressive strengths of the three samples at each ofthe three ash and/or dust contents on a chart of compressive strengthversus stabilizer content. Select the ash and/or dust content in thesame manner as used for selecting lime content in Step 5 under theheading “Lime and/or Hydrated Lime Stabilization” above.

Stabilization with Combinations of Portland Cement, Lime, and/orHydrated Lime with Fly Ash, Cement Kiln Dust, and/or Lime Kiln Dust

[0106] 1. Single Stage Type

[0107] Step 1.1

[0108] Based on Table 1, determine target contents for each of the limegroup and the ash/dust group. The combinations of lime and Class F flyash in Table 1 are based on the amount of fly ash required to provide apozzolan source and, secondly, the amount of lime required tosufficiently activate the Class F ash. However, if more plastic cuttingsare encountered and do not react with the lime group alone to providesufficient strength gain, then the lime group content may have to beincreased above that listed in Table 1 in order to modify the claycontent of the particulate mixture comprising drilling cuttings to bestabilized prior to activating the pozzolanic reaction with the Class Fash.

[0109] Step 1.2

[0110] Prepare samples according to ASTM D-698 to determine a predictedoptimum moisture content for a sample with each combination of limegroup and ash/dust group content selected in Step 1. Samples should beintimately mixed with both the lime group and the ash/dust groupstabilizers. The stabilizers of both groups may be added at the sametime unless the plasticity index of the cuttings as determined accordingto ASTM Procedure D-4318 exceeds 15 percent. In that instance, the limegroup stabilizer should be mixed first with the particulate mixturecomprising drilling cuttings to be stabilized, immediately followed bythe ash/dust group stabilizer.

[0111] Step 1.3

[0112] Fabricate three samples at and/or within 2% of the predictedoptimum moisture content determined in Step 2 for each trial contentcombination. Cure the samples by placing them in a sealed plastic bagand place the bagged samples in an oven or curing room at a temperatureof 40° C. for 7 days.

[0113] Step 1.4

[0114] Determine the unconfined compressive strength (UCS) of thesamples cured in Step 3 by the same procedures as for Step 4 under theheading “Lime and/or Hydrated Lime Stabilization” above.

[0115] Step 1.5

[0116] Plot the compressive strengths of the three samples at each ofthe three contents combinations on a chart of compressive strengthversus stabilizer content. Select the lime group and ash/dust groupcontents in the same manner as used for selecting lime content in Step 5under the heading “Lime and/or Hydrated Lime Stabilization” above.

[0117] 2. Two Stage Type

[0118] Step 2.1

[0119] The purpose of the initial step is to select a drying andpre-stabilization agent (hereinafter usually abbreviated as “DPSA”) thathas the capability of drying the drill cuttings to a level of acceptableworkability and of initiating the stabilization process. Typicalcandidates for DPSA include fly ash, lime kiln dust, cement kiln dust,and quicklime. The DPSA candidates should be able to produce a highenough pH to initiate a pozzolanic reaction between silica and aluminain the cuttings and calcium from the DPSA. This pozzolanic reactionaccomplishes part of the drying process and begins the strength gainprocess. Proper selection of the DPSA permits successful drying andstabilization. Within these constraints, the selection of theappropriate DPSA is largely based on site-specific availability and costeffectiveness.

[0120] Step 2.2

[0121] Mix trial amounts of the candidate DPSA with the cuttings intheir natural moisture state. The mixing process should simulate thelevel of preliminary mixing that can be achieved in the field. Areasonable process is to mix the DPSA with the cuttings in a mixing bowlwith a spatula. Then allow the mixture of cuttings and DPSA to dryovernight and test the resulting moisture content. A satisfactory levelof drying is achieved when the cuttings can be molded into a cohesivemass in the palm of a normal human hand. (This is typically at aboutthree to five percentage points above optimum moisture for compactionaccording to American Association of State Highway and TransportationOfficials Procedure T-99, if some soil is to be blended with the mixturein the final structure to be built according to the invention.)

[0122] Step 2.2′

[0123] (Used Only When Soil is to be Added to the Mixture in the FinalStructure to be Built According to the Invention.)

[0124] Blend samples of the dried mixture from step 2.2 with severalproportions of the soil to be used. Determine the moisture densityrelationship of the blend of cuttings, DPSA, and soil. A reasonablemoisture-density relationship according to American Association of StateHighway and Transportation Officials Procedure T-99 normally should beachieved with about five samples.

[0125] Step 2.3

[0126] Determine the type and amount of second stage stabilizer,alternatively denoted as “activator”, to be used. The activator can bethe same material as the DPSA, but typically will be Portland Cement orlime (calcium oxide or calcium hydroxide). The primary role of theactivator is to react with the soil and/or DPSA pozzolans to completethe pozzolanic reaction and to augment the pozzolanic reaction by ahydration cementitious reaction as required to achieve the desiredcompressive strength. The activator not only completes the stabilizationprocess but also completes the drying process.

[0127] Step 2.4

[0128] Determine the amount of the activator selected in Step 2.3 thatis needed to achieve the required unconfined compressive strength. Thedetermination can usually be effectively begun by molding three samplesat the predicted optimum moisture content determined in step 2.2(including 2.2′ if this step is used) and three additional samples ateach of one percent less than optimum and one percent in excess ofoptimum. Nine samples according to this procedure should be made foreach of the mixtures without activator and for activator contents ofeach of 3.0, 5.0, and 7.0 percent. The UCS of these samples is testedafter curing and conditioning as described for Steps 3 and 4 under theheading “LIME AND/OR HYDRATED LIME STABILIZATION” above.

[0129] Step 2.5

[0130] Select an appropriate mixture design based on the results of UCSTesting in Step 2.4. The UCS is used in a layered elastic model of thestructure to be built according to the invention as described in thesection of this description below after the heading “TARGET ENGINEERINGPROPERTIES AND STRUCTURAL THICKNESS REQUIREMENTS”.

Stabilization with Asphalt (Emulsidied and/or Foamed)

[0131] Step 1

[0132] Select a slow setting (hereinafter usually abbreviated as “SS”)emulsion for cuttings having greater than 15 percent by mass of materialpassing a sieve with openings 0.075 millimeter(s) (hereinafter usuallyabbreviated as “mm”). Otherwise, select a medium setting (hereinafterusually abbreviated as “MS”) emulsion. (A determination of whether ananionic or cationic emulsion should be used is based on coating andadhesion tests described in subsequent steps).

[0133] Step 2

[0134] Determine a trial emulsion and/or foam content for theparticulate mixture comprising drilling cuttings to be stabilized asfollows:

% emulsion and/or foam=[(0.06×B)+(0.01×C]×100)/A,

[0135] where A is percent residue by ASTM D-244, B is percent of driedparticulate mixture comprising drilling cuttings to be stabilized thatpasses a No. 4 sieve, and C is (100−B).

[0136] Step 3

[0137] The trial emulsion and/or foam content determined in Step 2 iscombined with the particulate mixture comprising drilling cuttings to bestabilized, corrected to a dry weight, and formed into a coating, whichis visually estimated as satisfactory or unsatisfactory for its intendeduse of the mix. The procedure for forming the coating consists of thefollowing operations: (3.1) Determine the moisture content of arepresentative particulate mixture comprising drilling cuttings to bestabilized; (3.2) mix in water by hand for 10 seconds or until visuallyuniformly dispersed, the amount of water being determined by visualinspection of the mixture; (3) add the selected weight of the trialemulsion and/or foam content to the moist aggregate at the anticipateduse temperature and mix vigorously by hand for 60 seconds or untilsufficient dispersion has occurred throughout the mixture; and (4) placethe mixture on a flat surface and visually estimate the degree ofcoating.

[0138] Step 4

[0139] Prepare three or more specimens each at a minimum of threedifferent emulsion and/or foam contents. If the mixture in the coatingtest of Step 3 appears satisfactory, use one specimen with the sameemulsion and/or foam concentration as used for Step 3, with one otherspecimen below and one other specimen above the trial emulsion and/orfoam content. If the mixture in the coating test of Step 3 appears to bedry, use one specimen with the foam and/or emulsion content used forStep 3 and increase the foam and/or emulsion content for each of theother two specimens. Conversely, if the mixture in the coating test ofStep 3 appears too wet, reduce the foam and/or emulsion content for thesecond and third specimens. (A normal difference between the emulsionand/or foam contents is one percent, or a residual asphalt contentdifference of 0.65 percent for an emulsion and/or foam with a 65 percentresidual content.)

[0140] Step 5

[0141] Determine adhesion by the following sequence of operations: (1)Cure a 100 gram portion of the mix from Step 4 in a shallow containerfor 24 hours in a forced draft oven at 60° C.; (2) put the oven-curedmix in a 600 milliliter (hereinafter usually abbreviated as “ml”) sizebeaker containing 400 ml of boiling distilled water; (3) bring to a boilagain, and maintain boiling and stir at one revolution per second; (4)pour off water and place the mix on a piece of white absorbent paper,and (5) after the mix has dried, visually evaluate the amount ofretained asphalt coating. If satisfactory, continue the mix design or ifnot acceptable, then the amount of emulsion and/or foam used should bemodified or another grade selected.

[0142] Step 6

[0143] Compact a freshly prepared specimen of the most satisfactorymixture(s) from Step 5 according to ASTM D 59 or D 1560. (Aeration ordrying of a dense-graded mixture is often required prior to specimencompaction. If the total liquid volume exceeds the voids in the mineralaggregate plus any absorbed liquid volume, proper compaction cannot beachieved.)

[0144] Step 7

[0145] Determine volumetrics and stability of the compacted mixtures.Volumetrics such as air voids, voids filled with bitumen, and voids inthe mineral aggregate, can be determined by properly accounting formoisture and following appropriate ASTM testing procedures, includingD-70, D-1188, D-2726, and D-3203. Marshall stability and flow should bedetermined following the procedures of ASTM D-1559 beginning atparagraph five (Procedure), except that the compacted specimenspreferably are placed in an air bath for a minimum of two hours at thetest temperature of 25° C. (±1° C.). A stability value of 2,224 N orgreater has been found to be satisfactory for most pavements with low tomoderate traffic volume. Hveem stability preferably is determinedfollowing ASTM D-1560 (paragraphs four through nine), except that thecompacted specimens preferably are placed in an air bath for a minimumof two hours at the test temperature of 25° C. (±1° C.). A stabilityvalue of 30 or greater has been found to be satisfactory for mostpavements with low to moderate traffic volume.

Target Engineering Properties and Structural Thickness Requirements

[0146] The combination of thickness and physical properties, e.g.,stiffness and strength, of the stabilized particulate mixture comprisingdrilling cuttings must be capable of supporting all of the continuousand/or varying loads applied to it during its designed use. For example,if the structure to be built by a process according to the invention isa drilling pad, the pad must be able to support heavy equipment hauledin and out of the site during the drilling operations. However,stiffness and strength values far greater than those needed aredisadvantageous for at least two reasons: very high stiffness andstrength values result in greater susceptibility to cracking and similarforms of brittle deterioration that can substantially shorten the usefullife of a structure, and achieving very high strength and stiffnessusually requires considerably larger fractions of stabilizer in astructure, thereby increasing its cost.

[0147] To assess the required engineering properties and thicknesscombinations required of the stabilized particulate mixture comprisingdrilling cuttings, a layered elastic structural evaluation is preferred.In this type of evaluation, the structure to be built is modeled as asuccession of layers. Each layer is modeled by a modulus and a Poisson'sratio with an assigned thickness. A load configuration is modeled tosimulate the critical traffic applied to the structure and includesconsideration of the wheel load, load geometries, and tire contactpressure. The layered elastic model (hereinafter usually abbreviated as“LEM”) calculates stresses and strains within the pavement system.Stresses and strains at critical points, e.g., compressive strains atthe top of the natural subgrade, and shearing stresses within thestructural layer are calculated and compared to criteria used to assessperformance in terms of the number of applications of such a design loadthat the structure can withstand.

[0148] A factorial LEM analysis was performed considering the effects offour variables: the number of load applications, subgrade strength,structural layer thickness, and structural layer strength and modulus.The design load was defined as an 18,000 pound single axle load, whichis expected to result in a structure that is fully satisfactorilystrong, stiff, and durable for a normal deep drilling pad or lease roadneeded in connection with deep drilling. Table 2 illustrates someresults of the factorial analysis. “E” in Table 2 represents theresilient modulus. The value for E given in Table 2 was calculated bythe most conservative of established empirical correlations betweenresilient modulus and UCS, specifically that:

E (in thousands of psi)≧0.12 (UCS {in PSI})+9.98.

[0149] The unit “thousands of psi” is hereinafter usually abbreviated as“kpsi”.

[0150] The UCS values shown in Table 2 are for samples that have beenmoisture-conditioned for 7 days. If unconditioned samples are usedinstead, the UCS values should be 100 psi higher than those shown inTable 2.

[0151] The control in Table 2 is a compacted crushed limestone gravelbase with a UCS value of 45 psi and a modulus that is expected to bewithin a range from 13 to 18 kpsi, based on typical properties ofunbound aggregate bases under a stress representative of that on astructural pad or a lease road.

[0152] A considerably higher UCS value than the maximum value of 300 psishown in Table 2 can be achieved by using high stabilizer percentages.However, the 300 psi value is considered to be the upper limitpractically required of most stabilized bases subjected to moistureconditioning that simulates the deep drilling field environment. Infact, if a stabilized layer can maintain at least 100 psi followingmoisture conditioning, it normally should provide adequate fielddurability when used in the thicknesses shown for that UCS value inTable 2. However, if the structure is being built in an area with acontinuously high water table or an area where there are large seasonalfluctuations in water table, a higher UCS value may be advantageous toprevent deterioration from these environmental influences. In a normaldeep drilling field environment, however, for the reasons given above,the UCS values obtained after 7 days of aging of the actual mixture ofmaterials to be used in building a structure by a process according tothis invention preferably does not exceed the value given in Table 2 forthe structure thickness and subgrade strength values as shown in Table 2by a percentage of said value given in Table 2 that is more than, withincreasing preference in the order given, 300, 250, 200, 190, 180, 170,160, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, or 20percent. For example, if the subgrade strength is at least 5,000 psi butless than 10,000 psi and the thickness of the structure to be built is16 inches, the conditioned UCS value preferably is at least 100 psi butneed not be more than 120 psi, but if the thickness is only 10 inches,the conditioned UCS value preferably is at least 300 psi and need not bemore than 360 psi. TABLE 2 FACTORS AND VALUES THEREOF CONSIDERED INFACTORIAL ANALYSIS AND RESULTING THICKNESS REQUIREMENTS Strength andStiffness of the Stabilized Particulate Mixture Recommended ComprisingParticles of “Control” or Thickness, Subgrade Strength of Soil, Rock, orBoth Rock and Soil inches Soft (E_(subgrade) = 5.0 kpsi) Control (E =13-18 kpsi) 18 UCS = 100 psi (E = 22 kpsi) 16 UCS = 200 psi (E = 35kpsi) 12 UCS = 300 psi (E = 47 kpsi) 10 Moderate (E_(subgrade) = 10.0kpsi) Control (E = 13-18 kpsi) 13 UCS = 100 psi (E = 22 kpsi) 12 UCS =200 psi (E = 35 kpsi) 9 UCS = 300 psi (E = 47 kpsi) 8 Strong(E_(subgrade) = 15.0 kpsi) Control (E = 12.6-18 kpsi) 8 UCS = 100 psi (E= 22 kpsi) 8 UCS = 200 psi (E = 35 kpsi) 8 UCS = 300 psi (E = 47 kpsi) 8

[0153] The thickness values recommended in Table 2 can accommodate atleast 10,000 applications of the design load with less than 1 inch depthof rutting. (These values were compared to those found using the U.S.Army Corps of Engineers granular base rutting model and found to be atleast as large as those recommended by that model.)

[0154] The thicknesses in Table 2 are exact only for the specifiedpurposes and conditions. Each instance of use of a process according tothis invention should be evaluated by the methods outlined above usingthe actual stabilizer(s) and particulate mixture comprising drillingcuttings to be stabilized and the particular strength, stiffness, anddurability requirements of the actual structure to be built.

[0155] In a particularly preferred embodiment of the invention, themixture comprising drilling cuttings provided in operation (1) of aprocess according to the invention as described above is a mixture thathas been produced by drilling through the surface of the earth to form aborehole by a process comprising suboperations of:

[0156] (1.1) providing drilling means, drilling driving means that causethe drilling means to operate at the bottom of said borehole, anddrilling mud; and

[0157] (1.2) causing said drilling driving means to drive said drillingmeans while said drilling mud flows into and out of said boreholethrough separate passageways disposed so as to insure that mud pumpedinto the borehole must reach the near vicinity of the drilling meansthat is deepening, widening, and/or otherwise increasing the volume ofsaid borehole before the mud can enter any passageway through which amixture of mud and cuttings flows out of the borehole during drilling,said mixture of mud and cuttings, optionally after removal therefrom ofall or part of the constituents of said mixture that are not cuttingsand/or additions thereto of other particulate material, constitutingsaid mixture that has been produced by drilling through the surface ofthe earth to form a borehole.

[0158] The invention may be further appreciated by consideration of thefollowing examples, at least some, but not necessarily all, of which areaccording to the invention.

EXAMPLES OF DEVELOPMENT OF STRUCTURAL STRENGTH IN MIXTURES INCORPORATINGDRILLING CUTTINGS Example 1

[0159] In this example, the cuttings used were obtained during drillingin the vicinity of Buffalo in Freestone County, Texas, using water-baseddrilling mud. The native soil in this area is described as follows bygovernment sources: “Edge Fine Sandy Loam, 5 to 12% Slopes. The EdgeSeries consists of deep over siltstone, well drained, very slowlypermeable upland soils. The surface to 11 inches is fine sandy loam. Thesubsoil is reddish and clay loam 11 to 29 inches.” Cuttings fromdrilling through this soil with a water-based drilling mud werecollected in a waste pit on the drilling site and allowed to settle fora period of at least several months. Settled and moist sediment of thistype was used as the cuttings to be stabilized during this example.These cuttings were determined by ASTM D 4318 to have an AtterbergLiquid Limit of 25, Plastic Limit of 16, and Plasticity Index of 9,while the native surface soil was independently determined to have anAtterberg Liquid Limit of 18 and Plastic Limit of 19.

[0160] Based on the principles given above, concentrations of 3, 5, and7% of Type 1 Portland Cement and a concentration of 10% of Class C FlyAsh were chosen as candidate stabilizers for a mixture of the selectedcuttings with twice its own mass of the native soil taken from the top12 inches thereof. In accordance with the Test Protocols given above forboth these stabilizers, a predicted optimum moisture content for eachmixture was determined according to ASTM D 698 for each mixture, withthe results shown in Table 3 below. TABLE 3 Predicted Optimum MoistureConcentration and Type of Stabilizer Percent 3% Cement 11.4 5% Cement10.6 7% Cement 11.0 10% Class C Fly Ash 9.6

[0161] Samples incorporating the predicted optimum moisture percent andmoisture percents differing from the predicted optimum by 2% bothgreater and less were then prepared and cured as described above in thetest protocols. The UCS values for these samples are shown in Table 4below. TABLE 4 UCS Value in psi with Percents of Moisture: Concentrationand Predicted Predicted Predicted Type of Stabilizer Optimum − 2 OptimumOptimum + 2 3% Cement 159 181 136 5% Cement 196 336 219 7% Cement 243389 358 10% Class C Fly Ash 28 54 40

[0162] In this instance, a UCS value expected to be satisfactory forvery heavy duty service is readily achieved with 5% or 7% cement and avalue satisfactory for slightly lighter duty service was achieved with3% cement. The particular type of Class C Fly Ash used was not aseffective in achieving strength gain as the cement.

Example 2

[0163] In this example, the cuttings used were obtained during drillingin Midland County, Texas, using water-based drilling mud. The nativesoil in this area is of two types, which are described as follows bygovernment sources: “Miles Loamy Fine Sand, 0 to 3% Slopes . . . TheMiles Series consists of deep, moderately drained soils on uplands . . .[From] 0 to 14 inches [the soil is/has] reddish-brown (5YR 5/4) loamyfine sand, dark reddish-brown (5YR 3/4) when moist; weak, very fine,subangular blocky structure; soft, very friable; common roots; neutral;gradual, smooth boundary” and “Sharvana Fine Sandy Loam, 0 to 3% Slopes.The Sharvana [S]eries consists of moderately permeable soils on uplands.These soils are shallow to indurated caliche . . . . In a representativeprofile the surface layer is reddish-brown fine sandy loam about 6inches thick. The next layer is reddish-brown sandy clay loam about 8inches thick.” Cuttings from drilling through this soil with awater-based drilling mud were collected in a waste pit on the drillingsite and allowed to settle for a period of at least several months.Settled and moist sediment of this type was used as the cuttings to bestabilized during this example.

[0164] Based on the principles given above, concentrations of 3, 5, and7% of Type 1 Portland Cement and a concentration of 10% of Class C FlyAsh were chosen as candidate stabilizers for a mixture of the selectedcuttings with twice its own mass of the native soil taken from the top12 inches thereof. In accordance with the Test Protocols given above forboth these stabilizers, a predicted optimum moisture content for eachmixture was determined according to ASTM D 698 for each mixture, withthe results shown in Table 5 below. TABLE 5 Predicted Optimum MoistureConcentration and Type of Stabilizer Percent 3% Cement 11.0 5% Cement11.5 7% Cement 11.0 10% Class C Fly Ash 10.5

[0165] Samples incorporating the predicted optimum moisture percent andmoisture percents differing from the predicted optimum by 2% bothgreater and less were then prepared and cured as described above in thetest protocols. The UCS values for these samples are shown in Table 6below. TABLE 6 UCS Value in psi with Percents of Moisture: Concentrationand Predicted Predicted Predicted Type of Stabilizer Optimum − 2 OptimumOptimum + 2 3% Cement 132 122 80 5% Cement 221 156 127 7% Cement 254 223161 10% Class C Fly Ash 115 80 63

[0166] In this instance, a UCS value expected to be satisfactory forvery heavy duty service is readily achieved with 5% or 7% cement and avalue satisfactory for slightly lighter duty service was achieved with3% cement. The particular type of Class C Fly Ash used was not quite aseffective in achieving strength gain as even the lowest percentage ofthe cement, but was much more effective than in Example 1.

Examples 3 to 9

[0167] In all of these examples, the cuttings used were obtained duringdrilling at various sites in Latimer County, Oklahoma using oil-baseddrilling mud. Cuttings from drilling through these soils with anoil-based drilling mud were passed over a shaker table and through acentrifuge in tandem to separate the cuttings from the drilling mud,which was recycled to drilling. Separated cuttings of this type wereused as the cuttings to be stabilized during these examples. Thesecuttings for Examples 5 to 9 were determined by ASTM D 4318 to haveAtterberg Liquid Limits, Plastic Limits, and Plasticity Indices as shownin Table 7 below, while the nearby surface soil was independentlydetermined to have values for the same characteristics at the time ofmixing with the cuttings used in the various examples as also shown inTable 7.

[0168] Based on the principles given above, concentrations of 3, 5, and7% of Type 1 Portland Cement and a concentration of a combination of 10%of Class C Fly Ash and 2% of Portland Cement were chosen as candidatestabilizers for the mixtures of the selected cuttings with twice theirown masses of the native soil taken from the top 12 inches thereof. Inaccordance with the Test Protocols given above for both thesestabilizers, an estimated optimum moisture content for each mixture wasdetermined according to ASTM D 698 for each mixture, with the resultsshown in Table 8 below. TABLE 7 Cuttings or Atterberg Test Values for:Example No. Soil? Liquid Limit Plastic Limit Plasticity Index 5 Soil 3122 9 Cuttings 55 45 10 6 Soil 56 28 28 Cuttings 31 26 5 7 Soil 20 71 3Cuttings 55 42 13 8 Soil 35 20 15 Cuttings 65 50 15 9 Soil 24 17 7Cuttings 48 39 9

[0169] Samples incorporating the predicted optimum moisture percent andmoisture percents differing from the predicted optimum by 2% bothgreater and less were then prepared and cured as described above in thetest protocols. The UCS values for these samples are shown in Table 9below.

[0170] In most of these instances, a UCS value expected to besatisfactory for moderately heavy duty service is readily achieved with5% or 7% cement. The combination of cement and the particular type ofClass C Fly Ash used, along with 3% cement only, was not as effective inachieving strength gain as the cement in most instances, but thecombination was nearly as good for Example 4. These results emphasizethat the exact materials to be used need to be tested and optimized inorder to achieve very highly satisfactory structures.

Examples 10 to 15

[0171] In these examples, the cuttings always included some cuttingsthat have been obtained by drilling with water-based mud. Therefore, inaccordance with the preferences indicated above, the processes accordingto the invention were divided into two stages. In the first stage, thecuttings and any mud of the same type used to produce them that hadpreviously been mixed for storage were mixed with a Class C Fly Ash, atype of stabilizer that is also a relatively inexpensive drying agent,to form a preliminary mixture. In the second stage, the preliminarymixture was itself mixed with soil from within the top 2 feet ofnaturally occurring soil near the site of the drilling operation thathad generated the cuttings and with Type I Portland Cement to form thefinal mixtures that were conditioned for several days TABLE 8Concentration and/or Predicted Optimum Moisture Example Number Type ofStabilizer Percent 3 3% Cement only 18.7 5% Cement only 17.0 7% Cementonly 18.4 Fly Ash + Cement 18.0 4 3% Cement only 20.4 5% Cement only19.5 7% Cement only 19.9 Fly Ash + Cement 18.6 5 3% Cement only 20.5 5%Cement only 19.9 7% Cement only 18.8 Fly Ash + Cement 18.6 6 3% Cementonly 18.9 5% Cement only 17.3 7% Cement only 14.0 Fly Ash + Cement 9.8 73% Cement only 15.0 5% Cement only 13.6 7% Cement only 14.1 Fly Ash +Cement 13.7 8 3% Cement only 16.0 5% Cement only 18.2 7% Cement only17.9 Fly Ash + Cement 15.5 9 3% Cement only 14.7 5% Cement only 14.6 7%Cement only 13.5 Fly Ash + Cement 12.8

[0172] TABLE 9 UCS Value in psi with Percents of Moisture: ExampleConcentration and/or Type of Predicted Predicted Predicted NumberStabilizer Optimum − 2 Optimum Optimum + 2 3 3% Cement only 73 82 63 5%Cement only 152 113 80 7% Cement only 215 229 160 Fly Ash + Cement 94 8761 4 3% Cement only 104 128 93 5% Cement only 128 172 160 7% Cement only191 226 184 Fly Ash + Cement 190 220 200 5 3% Cement only 92 75 50 5%Cement only 156 104 92 7% Cement only 172 122 119 Fly Ash + Cement 44 3732 6 3% Cement only 46 53 35 5% Cement only 48 66 72 7% Cement only 8962 141 Fly Ash + Cement 17 33 55 7 3% Cement only 105 73 60 5% Cementonly 218 166 119 7% Cement only 294 189 157 Fly Ash + Cement 117 90 57 83% Cement only 84 55 44 5% Cement only 116 97 76 7% Cement only 142 147101 Fly Ash + Cement 140 80 58 9 3% Cement only 87 59 57 5% Cement only118 125 82 7% Cement only 172 142 127 Fly Ash + Cement 170 109 102

[0173] before strength testing as described above. Except for Examples11, 14, and 15, the nearby surface soil that was used in the immediatelypreviously described mixtures was also mixed with Class C Fly Ash andwith at least some of the same fractions of the same type of PortlandCement as had been used to make these immediately previously describedmixtures, in order to determine whether the incorporation of cuttingswould change the strength values that could be obtained with soil, flyash, and cement alone. (These mixtures that contained no drillingcuttings are not examples according to the invention.)

[0174] Table 10 below gives further details of Examples. 10-15. TABLE 10Location % by Mass of All Constituents in Conditioned Mixture Except Ex-(North Portland Cement am- Latitude| Soil Only or Water-Based CuttingsOil-Based Cuttings ple West Mixture with and Any Mud Mixed and Any MudMixed Fly No. Longitude) Cuttings? Soil with Them in Storage with Themin Storage Ash 10 30°36.0′| Soil 80 0 0 20 91°30.5′ Mixture 50 30 12 811 32°58.3′| Mixture 71 24 0 5 97°23.1′ 12 33°8.1′| Soil 65 0 0 3597°22.2′ Mixture 71 21 0 7 13 33°10.6′| Soil 70 0 0 30 97°18.4′ Mixture71 22 0 7 14 33°10.0′| Mixture 71 26 0 3 97°18.2′ 15 32°58.3′| Mixture72 25 0 4 97°22.5′

[0175] Some of the mixtures as described in Table 10 were then mixedwith 3.0, 5.0, and 7.0 percent of their own mass of Type I PortlandCement. The predicted optimum moisture percent values for some of thesemixtures were determined in accordance with the procedures specifiedabove. Results are shown in Table 11 below. TABLE 11 Concentration ofPredicted Optimum Moisture Example Number Cement Percent 10 3% 22.0 5%20.9 7% 20.3 11 5% 24.1 12 5% 24.2 13 5% 19.5 14 5% 18.8 15 5% 23.1

[0176] Samples incorporating the predicted optimum moisture percent andmoisture percents differing from the predicted optimum by 2% bothgreater and less were then prepared and cured as described above in thetest protocols. For Examples 11 through 15, the predicted optimum for amixture with 5% of cement was used irrespective of the actual percent ofcement in the sample tested. The UCS values for these samples are shownin Table 12 below. These values were determined after 7 days ofconditioning for Examples 10, 14, and 15 and after 5 days ofconditioning for Examples 11 through 13.

[0177] In Examples 10 and 12, the mixtures containing cuttings developedsubstantially greater UCS values under most of the conditions testedthan the compared mixtures without cuttings, even though the lattercontained more of the fly ash stabilizer. TABLE 12 Cuttings Present UCSValue in psi with Percents of Moisture: Example Concentration of inConditioned HPredicted Predicted Predicted Number Cement Mixture?Optimum − 2 Optimum Optimum + 2 10 3% No 109 77 55 Yes 128 107 84 5% No160 103 59 Yes 153 127 113 7% No 164 90 63 Yes 169 135 117 11 3% Yes 113135 80 5% Yes 161 170 155 7% Yes 217 189 198 12 5% No 166 144 163 Yes264 264 223 7% Yes 342 318 249 13 3% Yes 129 83 not tested 5% No 278 257not tested Yes 148 113 85 7% Yes 137 113 75 14 3% Yes 133 123 71 5% Yes181 169 156 7% Yes 219 219 150 15 3% Yes 133 107 64 5% Yes 223 155 1477% Yes 250 207 146

CONSTRUCTION OF A WORKING LEASE ROAD INCORPORATING CUTTINGS BY A PROCESSACCORDING TO THE INVENTION

[0178] A volume of about 573 cubic meters (hereinafter usuallyabbreviated as “m³”) that was constituted preponderantly of cuttingsformed by drilling with an oil-based drilling mud and also included somefluidized bed fly ash (a material containing about 16% stoichiometricequivalent as SO₃ of sulfur) that had been added to the cuttings as adrying agent was used as the initial mixture comprising soil, rock, orboth rock and soil to begin the process according to this invention.Analysis showed that this initial mixture contained 9.9 ppt of solublesulfate and 86 ppt of total petroleum hydrocarbons and had a bulkdensity of 1.4 megagrams per cubic meter (hereinafter usuallyabbreviated as “Mg/m³”). Because this initial mixture contained too muchsulfate for direct use in a process according to the invention asdescribed above, the initial mixture was diluted with some of the nativesoil in this area, which is described as “Bengal-Denman association,moderately steep” by the U.S. Department of Agriculture SoilConservation Service, (now named the Natural Resources ConservationService). Further details about this soil are available in Soil Surveyof Latimer County, Oklahoma, Issue of December 1981. This soil wasanalyzed and found to contain 1.23 ppt of soluble sulfate and 15 ppt oftotal organic carbon and to have a bulk density 1.5 Mg/m3. Calculationshows that this soil can be mixed in a bulk volume ratio of 7:3 with theinitial mixture of cuttings and fluidized bed fly ash to form an amendedinitial mixture with no more than 3 ppt of sulfate. Because this isstill near the upper limit of sulfate that can be treated in a processaccording to this invention without concern, Portland Cement wasselected as the stabilizer for use in the process according to theinvention, inasmuch as Portland Cement is the most tolerant of sulfateof all the lime-based stabilizers shown in Table 1, and in particular“ASTM C 150, Type II” cement, a sulfate-tolerant type of cement, wasselected. Consideration of Table 1 shows that 6.0 ppt of the cementshould produce a satisfactory final structure.

[0179] Accordingly, the Bengal-Denman soil noted above was mixed with avolume fraction of 4% of the soil volume with this type of cement toform a combined stabilizer-diluent mixture. This mixture, because thecement has a bulk specific gravity of 3.14, contained 7.8 ppt of thecement.

[0180] A layer of the initial mixture containing oil-based cuttings andhigh sulfate as noted above, the layer being about 0.15 meters in depthand from 11 to 14 meters in width, was deposited along the line of theroad to be constructed, and then covered with a second layer of thestabilizer-diluent mixture described above, this second layer beingabout 0.46 meters in depth and the same width as the first layer. Theentire particulate contents of these two layers were then mixed with asoil stabilizer machine, a machine that is known in the art to achieveexcellent mixing throughout the entire depth of particulates mixed.Sufficient water was then added atop this mixture to provide an amountof water by mass equal to 12 to 14% of the mass of the mixture, andafter a pause of 30 minutes to allow the water to permeate through thedepth of the particulate bed, the top of the bed was successively rolledwith a “sheep's foot roller” that applied a pressure of 200 to 300pounds per square inch, bladed, and rolled with a smooth roller whichapplied very little pressure and acted essentially as a finishing tool.A thickness of 0.4 centimeter of gravel was then spread over the top ofthe thus prepared road bed. All of these operations for the entire roadconstruction were completed within three hours after the mixing of thestabilizer-diluent mixture with the initial mixture had begun.

[0181] Within two days after the construction as described above of astructure intended to serve as a road was completed, the structure beganto be used as a road, and in over four months of service it has shown noevidence of deterioration of any type, including rutting, despitefrequent passage over the road of tractor-trailer trucks and their loadstotaling about eighty thousand pounds for each truck. There was heavyrain during this period, and conventional lease roads, consistingessentially of several inches thickness of gravel, that were in the samearea and subjected to the same level of traffic loads needed frequentre-graveling to reduce rutting. Thus the road constructed by a processaccording to the invention demonstrated clearly superior quality.

The invention claimed is:
 1. A process for constructing load-bearingstructures incorporating drilling cuffings, said process comprisingoperations of: (1) forming a particulate mixture comprising drillingcuttings; and (2) at least one of groups (2.1) and (2.2) ofsuboperations, said group (2.1) comprising suboperations of: (2.1.1)mixing said particulate mixture comprising drilling cuttings in aspecified proportion with at least one stabilizer selected from thegroup consisting of: (A) quicklime; (B) hydrated lime; (C) PortlandCement; (D) Class C fly ash; (E) cement kiln dust; (F) lime kiln dust;(G) Class F fly ash; and (H) other pozzolans to form a cementitioussecond mixture; (2.1.2) forming said cementitious second mixture intothe shape and size of the desired load-bearing structure; and (2.1.3)causing the shaped and sized second mixture formed in suboperation(2.1.2) to undergo a pozzolanic reaction to form said load-bearingstructure; and said group (2.2) comprising suboperations of: (2.2.1)mixing said particulate mixture comprising drilling cuttings in aspecified proportion with at least one of foamed asphalt and emulsifiedasphalt to form an asphaltic second mixture; (2.2.2) forming saidasphaltic second mixture into the shape and size of the desiredload-bearing structure; and (2.2.3) causing the shaped and sizedasphaltic second mixture formed in suboperation (2.2.2) to form theload-bearing structure by removal from said shaped asphaltic secondmixture of a sufficient fraction of the gas dispersed in any foamedasphalt incorporated into said second mixture and of the liquidcontinuous phase in which any emulsified asphalt incorporated into saidshaped second mixture is emulsified.
 2. A process according to claim 1,wherein at least 10 percent by mass of said particulate mixture are deepdrilling cuttings that have been generated by a process comprising thefollowing suboperations: (1.1) providing drilling means, drillingdriving means that cause the drilling means to operate at the bottom ofa borehole, and drilling mud; and (1.2) causing said drilling drivingmeans to drive said drilling means while said drilling mud flows intoand out of said borehole through separate passageways disposed so as toinsure that mud pumped into the borehole must reach the near vicinity ofthe drilling means that is deepening, widening, and/or otherwiseincreasing the volume of said borehole before the mud can enter anypassageway through which a mixture of mud and cuttings flows out of theborehole during drilling, said mixture of mud and cuttings, optionallyafter removal therefrom of all or part of the constituents of saidmixture that are not cuttings, constituting said deep drilling cuttings.3. A process according to claim 2, wherein at least part of the deepdrilling cuttings have been produced by drilling with a water-baseddrilling mud.
 4. A process according to claim 3, said process comprisinggroup (2.1) of suboperations.
 5. A process according to claim 4, whereinsaid stabilizer is selected from the group consisting of quicklime,hydrated lime, Portland Cement, Class C fly ash, and mixtures of Class Cfly ash with Portland Cement.
 6. A process according to claim 5,wherein: said stabilizer is a mixture of Class C fly ash with PortlandCement; and suboperation (2.1.1) is accomplished in two stages, in thefirst of which Class C fly ash is mixed with said particulate mixturecomprising drilling cuttings and in the second of which Portland Cementis mixed into the mixture previously formed by mixing Class C fly ashwith said particulate mixture comprising drilling cuttings.
 7. A processaccording to claim 6, wherein, based on the particulate mixturecomprising drilling cuttings to be stabilized: the amount of PortlandCement used as a stabilizer is at least 1.0%; the amount of Class C flyash used as a stabilizer is at least 2.0%; and the ratio of the amountof Class C fly ash used as a stabilizer to the amount of Portland Cementused as a stabilizer is at least 0.50:1.0 but is not more than 10:1.0.8. A process according to claim 2, wherein at least part of the deepdrilling cuttings have been produced by drilling with an oil-baseddrilling mud.
 9. A process according to claim 8, said process comprisinggroup (2.1) of suboperations.
 10. A process according to claim 9,wherein said stabilizer is selected from the group consisting ofquicklime, hydrated lime, Portland Cement, Class C fly ash, fluidizedbed fly ash, and mixtures of either Class C or fluidized bed fly ashwith Portland Cement.
 11. A process according to claim 10, wherein: saidstabilizer is a mixture of Class C or fluidized bed fly ash withPortland Cement; and suboperation (2.1.1) is accomplished in two stages,in the first of which C fly ash is mixed with said particulate mixturecomprising drilling cuttings and in the second of which Portland Cementis mixed into the mixture previously formed by mixing fly ash with saidparticulate mixture comprising drilling cuttings.
 12. A processaccording to claim 11, wherein said load-bearing structure has anunconfined compressive strength of at least 100 psi and has a thicknessof: at least 8 inches if constructed on a subgrade with a resilientmodulus that is at least 15.0 kpsi; at least 12 inches if constructed ona subgrade with a resilient modulus that is at least 10.0 kpsi but lessthan 15.0 kpsi; and, at least 16 inches if constructed on a subgradewith a resilient modulus that is at least 5.0 kpsi but less than 10.0kpsi.
 13. A process according to claim 10, wherein said load-bearingstructure has an unconfined compressive strength of at least 100 psi andhas a thickness of: at least 8 inches if constructed on a subgrade witha resilient modulus that is at least 15.0 kpsi; at least 12 inches ifconstructed on a subgrade with a resilient modulus that is at least 10.0kpsi but less than 15.0 kpsi; and, at least 16 inches if constructed ona subgrade with a resilient modulus that is at least 5.0 kpsi but lessthan 10.0 kpsi.
 14. A process according to claim 7, wherein saidload-bearing structure has an unconfined compressive strength of atleast 100 psi and has a thickness of: at least 8 inches if constructedon a subgrade with a resilient modulus that is at least 15.0 kpsi; atleast 12 inches if constructed on a subgrade with a resilient modulusthat is at least 10.0 kpsi but less than 15.0 kpsi; and, at least 16inches if constructed on a subgrade with a resilient modulus that is atleast 5.0 kpsi but less than 10.0 kpsi.
 15. A process according to claim6, wherein said load-bearing structure has an unconfined compressivestrength of at least 100 psi and has a thickness of: at least 8 inchesif constructed on a subgrade with a resilient modulus that is at least15.0 kpsi; at least 12 inches if constructed on a subgrade with aresilient modulus that is at least 10.0 kpsi but less than 15.0 kpsi;and, at least 16 inches if constructed on a subgrade with a resilientmodulus that is at least 5.0 kpsi but less than 10.0 kpsi.
 16. A processaccording to claim 5, wherein said load-bearing structure has anunconfined compressive strength of at least 100 psi and has a thicknessof: at least 8 inches if constructed on a subgrade with a resilientmodulus that is at least 15.0 kpsi; at least 12 inches if constructed ona subgrade with a resilient modulus that is at least 10.0 kpsi but lessthan 15.0 kpsi; and, at least 16 inches if constructed on a subgradewith a resilient modulus that is at least 5.0 kpsi but less than 10.0kpsi.
 17. A process according to claim 4, wherein said load-bearingstructure has an unconfined compressive strength of at least 100 psi andhas a thickness of: at least 8 inches if constructed on a subgrade witha resilient modulus that is at least 15.0 kpsi; at least 12 inches ifconstructed on a subgrade with a resilient modulus that is at least 10.0kpsi but less than 15.0 kpsi; and, at least 16 inches if constructed ona subgrade with a resilient modulus that is at least 5.0 kpsi but lessthan 10.0 kpsi.
 18. A process according to claim 3, wherein saidload-bearing structure has an unconfined compressive strength of atleast 100 psi and has a thickness of: at least 8 inches if constructedon a subgrade with a resilient modulus that is at least 15.0 kpsi; atleast 12 inches if constructed on a subgrade with a resilient modulusthat is at least 10.0 kpsi but less than 15.0 kpsi; and, at least 16inches if constructed on a subgrade with a resilient modulus that is atleast 5.0 kpsi but less than 10.0 kpsi.
 19. A process according to claim2, wherein said load-bearing structure has an unconfined compressivestrength of at least 100 psi and has a thickness of: at least 8 inchesif constructed on a subgrade with a resilient modulus that is at least15.0 kpsi; at least 12 inches if constructed on a subgrade with aresilient modulus that is at least 10.0 kpsi but less than 15.0 kpsi;and, at least 16 inches if constructed on a subgrade with a resilientmodulus that is at least 5.0 kpsi but less than 10.0 kpsi.
 20. A processaccording to claim 1, wherein said load-bearing structure has anunconfined compressive strength of at least 100 psi and has a thicknessof: at least 8 inches if constructed on a subgrade with a resilientmodulus that is at least 15.0 kpsi; at least 12 inches if constructed ona subgrade with a resilient modulus that is at least 10.0 kpsi but lessthan 15.0 kpsi; and, at least 16 inches if constructed on a subgradewith a resilient modulus that is at least 5.0 kpsi but less than 10.0kpsi.